


Un-eggs-spected

by Tsaiko



Category: Undertale (Video Game)
Genre: Anxiety, Bodily Fluids, Egg Laying, Egg Laying Occurs in Story, Sex Talk, Soul Bond, Strange Reproduction Strategies, Unplanned Pregnancy, Weird Biology
Language: English
Status: In-Progress
Published: 2018-06-10
Updated: 2018-10-14
Packaged: 2019-05-20 13:47:35
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,622
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14895735
Author URL: https://archiveofourown.org/users/Tsaiko/pseuds/Tsaiko
Summary: Sans had no idea he was gravid until he unexpectedly laid an egg in the kitchen at 2am. Honestly, stranger things had happened in his life.





	1. Chapter 1

**Author's Note:**

> 1500 words of Sans laying an egg in the kitchen. Why? Because we have no idea how skeleton monsters reproduce and I could not get this mental image out of my head. Even stranger I don't read for this fandom, haven't played this game, and everything I know about it comes from a) watching Cryaotic do a play through, b) the Undertale Wiki, and c) my lovely wife. So yeah... 
> 
> Also, please mind the tags.

At 2am, Sans decided to go into the kitchen. 

If asked, he wouldn't have been able to tell you why the kitchen. Maybe some vague notion of making himself warm milk to get back to sleep. Sans hadn't made himself or Papyrus warm milk in years, but the idea of it was comforting. Something to soothe the edge that itched across his bones lately. 

He'd gone to bed naked, because lately even clothes seemed to be _too much._ Too much effort. Too much sensation. Too much heat. Sans didn't dare wander around the house naked though because if Papyrus caught him, he would never hear the end of it. So when Sans wandered into the kitchen it was in a tatty looking bathrobe and his normal house slippers. No, they didn't match. 

The light was too bright, but Sans didn't feel like stumbling around in the dark. He headed towards the fridge. That had been his intent, right? To get milk? Inside the fridge were several containers of "spaghetti," two bottle of ketchup, a gallon of milk, a slice of pie courtesy of Toriel, and a wilted head of lettuce that was quickly changing from green-ish to definitely brown. 

Milk. He'd come here to get milk. Hadn't he? Sans was no longer sure what had driven him to go to the kitchen so late at night. Inertia seemed to be the way to go though, so Sans picked up the milk jug. Reaching caused an uncomfortable twinge to go through the base of his spine. That had been happening a lot lately. He'd gotten use to ignoring it. 

Was the milk still good? Sans couldn't remember when he or Papyrus had bought the milk. Probably the last time Frisk had visited. He took the top off and smelled. It still smelled okay at least. 

Then everything went dark around the edges as pain hit, starting at the base of his spine and radiating outwards. Sans doubled over, arms wrapping protectively across his middle by instinct. The plastic jug of milk hit the floor with an underwhelming whump, and immediately started spilling milk everywhere. He stumbled across the small kitchen, heading vaguely towards the trashcan. If he was going to be sick, he could at least contain the mess. Pain drove him to his knees just as he reached it. 

The checkerboard patterned tile blurred together. Sans knocked the trashcan out of the way. He half shuffled, half crawled over to the corner until his back was pressed against the wall. Instinct drove him into a weird squatting position even though his legs shook with the effort of keeping him upright. 

Fluid came out from under the robe in a rush of warmth. No. Not fluid. Concentrated magic. It glowed electric blue as it hit the floor. Sans used the wall to brace himself as his entire body tightened. There was more magic fluid, a painful shift as bones in his pelvic girdle rearranged, and then a horrible increase in tension. He wanted to scream, but what came out was more like a moan. 

The pressure built. Sans panted. Another push. More pressure. 

Then something released. There was another flow of magical fluid, a shift inside him, and the sound of something _plopping_ into the puddle on the floor. The effect was immediate. Sans felt his pelvic girdle rearrange itself again, but there was no pain. Just some uncomfortable shifting and a dull ache where something use to be. He stumbled forward two steps, sank down onto his knees, and looked to see what had happened. 

An egg. There was an egg. Sans had laid an egg. He'd been gravid? How? He moved closer, heedless of the magic seeping into his robe and staining the hem blue. 

The egg was dark in color – not quite blue, not quite black – with a spider web of cracks that leaked blue magic. Sans carefully traced one finger along the shell. It was leathery in texture and yielded a little under his touch. Still soft. The magic pulsed slightly and Sans could feel a surge of warmth in the soul in his chest. His child recognized him. 

"hey little one. Are you eggs-cited to be here?" His soul fluttered and Sans felt tears sting in his eye sockets. 

"SANS? WHERE ARE YOU? I HEARD A NOISE." 

Sans whirled from where he'd been examining the egg. Power crackled around him, and a blue haze fell across his vision. He heard the faint hum of the bone dragon skulls he'd summoned circling around him. 

It was still soft. Still vulnerable. Sans had to protect the egg. 

"THERE YOU ARE. IT IS THE MIDDLE OF THE NIGHT. WHY ARE YOU IN..." Papyrus's voice tapered off as he took in the situation. His eye sockets went wide. 

Sans tried to get his emotions under control. This was Papyrus. His brother. There was no need for him to protect the egg. Still, his vision remained washed in blue. The bone dragon skulls circled ominously. 

"REALLY SANS? IN THE KITCHEN? YOU COULDN'T HAVE LAID YOUR EGG IN YOUR ROOM LIKE A SENSIBLE SKELETON?" Papyrus said. The complaint was so completely _Papyrus_ that Sans felt himself chuckling and relaxing. The bone dragon skulls faded from reality. Papyrus made no move to enter the kitchen even with them gone. "WHY DIDN'T YOU TELL ME YOU WERE GRAVID?" 

How could he have told Papyrus when he hadn't known himself? Maybe he should have guessed. Sans knew all the signs from the horrible "talks" Gaster had given him and Papyrus about skeleton monster biology. They included: 

  * Excessive sleeping or lethargy.
  * Increased appetite.
  * Craving high calorie foods.
  * Gaining weight.
  * Nesting behaviors such as:
    * Rearranging items multiple times.
    * Not wanting to leave a specific room.
    * Hording one type of item.
    * Efforts to keep others out of the room.
    * Urges to clean.
  * Wanting to stick to one routine.
  * Increased sensitivity to temperature changes.
  * Irritation.



The signs of being gravid were pretty much Sans's life in a nutshell. Some of them hadn't even happened to him. He'd had no urge to clean unless you counted throwing a can of soda vaguely in the direction of the trash tornado. His irritation had most been directed at his clothes, not people. Gaster's irritation had definitely been directed at people when Gaster was gravid with Papyrus. Sans had had no urge to stick to one routine. The only real indication was the pillow hording, but he'd thought Papyrus's complaining was hilarious. 

"i..." Sans started, and then immediately stopped. He hadn't know he was gravid, but it wasn't something he wanted to admit just yet. "i thought it would make an eggs-cellent surprise." 

"YOU COULD HAVE AT LEAST BUILT A NEST FOR IT. NOT LEFT IT ON THE KITCHEN FLOOR," Papyrus replied. He left the kitchen. Sans felt an instant relief and then felt bad he was relieved that Papyrus was gone. 

It didn't stop him from tensing again when Papyrus came back into the kitchen. He had several towels in his hands. "I'M JUST GOING TO CLEAN UP THE MILK. DO YOU WANT ME TO GRAB SOME BLANKETS AND PILLOWS, OR DO YOU WANT TO GET THEM?" 

Leave the egg? While it was so vulnerable? Sans felt the blue wash over his vision again and sighed. He was going to sleep for a week expending so much energy right after laying. "i'm going to be sticking close to it. at least until it hardens. i can sleep on the floor." 

"BECAUSE THAT IS SO CONDUCTIVE TO RESTFUL SLEEP." Papyrus was sopping up the last of the milk. He turned to Sans, dripping towels in his hands. "YOU KNOW I WOULD FIGHT ANYONE WHO WOULD DARE MESS WITH MY NEW NIBLING. YOU ARE NOT ALONE IN THIS, SANS." 

"i hope it won't come to that, bro." Still, the knowledge eased some of the worry in him. The blue faded from his vision once more. "

"REGARDLESS, THAT IS THE TRUTH." Papyrus left the kitchen. Sans could hear him rummaging around the house. He soon returned with several pillows that he dropped in a pile on the kitchen floor. When Papyrus left again, Sans started grabbing them up and arranging them around the egg. The fluid had already dried to a tacky consistency. The cracks in the shell were fading as it hardened. "BLANKETS. I WOULD TELL YOU TO GET SOME REST, BUT I KNOW YOU WILL." 

"there's no reason i can't watch the egg and sleep at the same time. it's called multi-tasking." Sans grabbed the blankets, arranging and rearranging them until he was satisfied at the nest. Papyrus sat cross legged on the tile floor. He didn't try to approach. Sans didn't invite him either. Not yet. Not when he was still grappling with the idea that the egg was his. 

"SO WHO IS THE LUCKY OTHER PARENT?" Papyrus asked. Sans looked at the egg, and then back at his brother. 

"i don't know, bro."


	2. Sneaking Suspicions

**Summary for the Chapter:**

> Where Papyrus gets to touch the egg, skeleton reproduction is a lot more complicated than it initially seems, Sans wishes his brother would stop saying the word "sex," and if Sans thinks Papyrus is going to drop the topic, he has another thing coming.

**Notes for the Chapter:**

> How many people thought they were going to get another 2100 words of this fic? I know I sure didn't. Notice the jump from 1 chapter to 5 chapters. That was news to me as well until I started plotting out more of it. Be aware of tag changes. More will be coming, especially given the next chapter.

It had taken Sans four days before he felt comfortable letting Papyrus touch the egg. It was ridiculous. Sans trusted Papyrus with his life. He should be fine with letting Papyrus touch his egg. In fact, Sans should be encouraging it. It was always a good idea for the little ones to get use to all members of their family while still in the shell. If he concentrated hard enough, Sans could remember that advice from when Papyrus was still an egg.

And yet... Sans couldn't help being overprotective. Maybe because this was his first egg? Most times Sans didn't miss Gaster, but he really wished he could ask him for information. There just hadn't been that many skeleton monsters left that he could ask for advice, and the few he knew of had moved as far away from Mt. Ebott as they could once they reached the surface. 

Once the magic fluid dried it effectively glued the egg to the kitchen floor. It would stay there until it hatched. Papyrus was right, though Sans would never admit it. Laying the egg in his room would have been less nerve wracking. If he'd laid it right next to the mattress, then Sans would have been able to check on it without leaving his bed. Which sounded like heaven compared to having to walk all the way downstairs or teleport to the kitchen when he grew too anxious.

There hadn't been a reset in seven years, ever since the monsters had come above ground and Frisk had promised him it wouldn't happen. Sans still had anxiety. He would probably always have anxiety. But it had been much, much better.

It had ratcheted right back up to eleven now that he had an egg.

The worst part was that part of the problem was Papyrus. Sans kept expecting him to bring up the issue that Sans didn't know who the other parent was. He was going to have to explain eventually. After all, as a skeleton Papyrus needed to know how skeleton reproduction worked. He just wasn't looking forward to it.

"SANS CAN I MOVE THE BLANKETS TO MOP AROUND THE EGG?" Papyrus asked. He was always careful to announce his intentions around the egg. 

"yeah, go ahead." Sans said from where he was seated on the couch. He had an almost clear line of sight to where Papyrus was moving around the kitchen. Even Sans was surprised by the next words that came out of his mouth. "you can touch it as well."

"REALLY?" Sans could hear Papyrus lean the mop against the kitchen wall. He did his best not to tense. "YOU KNOW I WILL BE VERY GENTLE. YOU CAN BREATHE."

Sans let out a breath he hadn't known he was holding. Breathe. He needed to breathe. Inhale. Hold. Exhale. Hold. It was a technique Sans had perfected over the years whenever things got to be too much.

He could see Papyrus moving in their small kitchen towards the corner where the egg was. It was too much. Anticipation and dread pressed heavy down on him, and Sans tilted his head back until all he could see was the ceiling. Looking for something to distract himself with. A spider was making a web in the corner and Sans wondered if it was a surface spider or an Underground one.

"OH." Something in Papyrus's tone made Sans look. His brother was sitting on the floor hand outstretched. Probably touching the egg. The other hand was pressed to his chest, where his soul would be. "IT IS HOT."

And just like that, it was okay.

"of course it's hot. look who laid it." Sans was delighted by Papyrus's groan. 

"REALLY SANS? THAT WAS TERRIBLE EVEN BY YOUR STANDARDS." Papyrus got to his feet. "I WAS NOT EXPECTING TO FEEL THAT IN MY SOUL."

"yeah. there's a bit of a soul bond because your family." Sans paused, wondering if he should bring up the past. Sometimes it just made Papyrus go blank. But it might be okay if he didn't mention Gaster. "you were like that with me when you were in the egg. i could feel you in my soul when you were in the shell."

"I DO NOT REMEMBER THAT," Papyrus said as he came into the living room. His hand was still resting on his chest, fingers pressing against the sweater he wore just above where his soul would be. "FAMILY IS IMPORTANT, SO IT MAKES SENSE." Papyrus came up behind the couch and rested his hand on Sans's shoulder. "SOMETIMES ALL YOU HAVE IS FAMILY." 

Sans felt a surge of warmth in his soul that had nothing to do with the egg. His brother was the best.

***

No one lived Underground any more. It had been a prison for monsters, and no one could really shake that feeling and call it home. That didn't mean that monsters never wanted to see it again. Or be close to it. So a thriving town had grown up on the slopes of Mt. Ebott. 

In the seven years since they'd left the Underground, Sans and Papyrus's house had become the go to social spot for their group of monster friends when it came to getting together. Sans wasn't sure how that had happened. They'd always been open to letting Undyne stay, and Sans had invited Toriel to drop by whenever she was in the area. Now that Alphys was no longer the royal scientist or felt like she had to hide in the lab, she often showed up as well. Especially when Undyne came over. Mettaton sometimes made an appearance, much to Papyrus's delight. Even Asgore stopped by every once in a while when he knew Toriel wasn't going to be there.

Which explained why Papyrus was on the phone, trying to lie to Undyne about why they couldn't host movie night. Only this was Papyrus. Sans loved his brother, but Papyrus didn't have the brain to mouth filter necessary to be a good liar.

"IT'S JUST REALLY NOT A GOOD TIME. SANS HAS... STARTED A NEW PROJECT. THE HOUSE IS REALLY NOT SET UP FOR GUESTS."

Sans snorted. "a project that will last a good eighteen years." Somehow that amount of time didn't seem that daunting. Most likely because the whole thing was still theoretical as long as the kid was still in the shell. Or maybe all those resets made long term plans seem kind of useless. Even if it had been years since one.

"HOW LONG WILL IT BE? I THINK ANYWHERE BETWEEN TEN AND TWELVE WEEKS. UNTIL THEN WE WILL NEED TO MEET AT SOMEONE ELSE'S HOUSE." There was a pause while Papyrur listened to Undyne. "YES, I TRIED TO GET HIM TO LIMIT THE MESS TO ONE ROOM, BUT THIS IS SANS. HIS MESS SPREADS."

"my mess has stayed with just me for years," Sans complained to no one in particular, and softly enough that Papyrus probably didn't hear. Probably. "so many untruths being told about me."

"WHAT IS THE PROJECT? UM. YES. I AM NOT EXACTLY SURE. IT INVOLVES A LOT OF SCIENCE-Y... UH... THINGS. IT'S ALL VERY INTERESTING I AM SURE. BUT THE MAIN THING IS THAT WE CANNOT HOST THIS WEEK AND POSSIBLE FOR SEVERAL WEEKS UNTIL IT IS DONE."

That didn't sound suspicious at all. This was why when it came to lying, Papyrus should just let Sans do it. He would have told his brother as much, but that would have implied Papyrus couldn't lie. Which would have made Papyrus insist on doing this. So either way, this terrible conversation with Undyne was going to happen.

"I SUPPOSE I COULD CLEAN UP AFTER HIM. I DO THAT ALL. THE. TIME." Yep, that statement was not directed towards Undyne. Sans huffed, but didn't argue. "I DON'T THINK I COULD DO IT QUICKLY ENOUGH FOR GUESTS."

"OH? COMING OVER TO YOUR HOUSE? UH. UM. I DON'T THINK WE CAN. SANS NEEDS TO MONITOR HIS PROJECT. MAYBE NEXT WEEK?" There was a pause where Undyne said something. "I DON'T KNOW WHY YOU WOULD THINK THAT. I ASSURE YOU NOTHING SUSPICIOUS IS GOING ON."

"OKAY. WE WILL SEE YOU NEXT WEEK." Papyrus hung up the phone, sat down beside Sans, put his head in his hands, and made the most undignified sound ever. Sans reached out and patted him on the shoulder. In response, Papyrus leaned over and pressed his weight against Sans.

"I DO NOT LIKE LYING LIKE THAT."

"why didn't you just tell her the truth?" Sans asked. "don't get me wrong. i don't want anyone over just yet, but they're going to find out about the egg eventually. it's un-eggs-pected but i'm not ashamed or anything."

"YOU SAID YOU DIDN'T..." Papyrus groaned at the pun. "REALLY SANS? ANYWAY, YOU SAID YOU DIDN'T KNOW WHO THE OTHER PARENT WAS AND I DIDN'T WANT TO PUT YOU IN A DIFFICULT SITUATION WHERE YOU MIGHT HAVE TO ANSWER QUESTIONS," Papyrus replied. 

Okay, yep. There was the mention of the other parent Sans had been expecting. It was talk time. Papyrus looked over at Sans. He saw something in Sans's expression, because Papyrus got the disappointed look on his face. "ALTHOUGH I KNOW YOU SANS. YOU HAVE NOT HAD SEX WITH ENOUGH PEOPLE TO NOT HAVE AN IDEA WHO THE OTHER PARENT MIGHT BE. I HIGHLY ENCOURAGE YOU TO TELL THEM EVEN IF YOU DON'T WANT TO. THEY DESERVE TO KNOW."

Sans winced. Well. This was awkward. Papyrus was several years younger than Sans and Gaster had been big on making his explanations on skeleton biology age appropriate. Unfortunately, that didn't mean that they were necessarily thorough. "the bonding between souls to create the egg didn't happen from... an intimate act."

Papyrus rolled his eyelights. "YOU CAN SAY SEX, SANS." That wasn't happening. "AND I'M PRETTY SURE THE BOOKS YOU GAVE ME ON ALL THINGS INTIMATE AS WELL AS MY DATING BOOK SAY THERE NEEDS TO BE TWO MONSTERS OR PEOPLE INVOLVED FOR THEIR TO BE AN EGG. OR A CHILD. WHICHEVER IS ANATOMICALLY APPROPRIATE."

"skeletons don't have as many barriers between the world and their souls. some of the other not quite corporal monsters like grillby or napstablook are the same. sometimes just being around someone you are affectionate with is enough for your soul to absorb some of their soul. it's not common for monsters to be born without intimate acts, but it happens.

"SERIOUSLY, JUST SAY THE WORD SEX SANS. THERE IS ANOTHER PARENT THEN?"

Nope. Not saying sex, and Sans honestly wished Papyrus would stop saying it as well. "it could be anyone. the only requirements is that i like them and have spent enough time around them to absorb some of their soul. no exchange of magic or fluids necessary."

"I'M BEGINNING TO THINK THAT YOUR REFUSAL TO CALL IT SEX STEMS FROM YOU PROJECTING YOUR ISSUES ON TO ME."

"don't know what you could possibly mean," Sans replied. He left his eyelights fade until his vision was dark and settled more comfortably into the sofa. Papyrus sighed as if the entire weight of the world was on his shoulders. "don't worry too much about it, bro. we'll probably never know."

There was a long moment of silence. Too much silence. Sans relit his eyelights so that he could look at Papyrus. "YOU DON'T HAVE TO HAVE SEX, BUT SOME SORT OF AFFECTION IS REQUIRED? SO YOU MUST HAVE SOME..."

"Papyrus." The word was in a tone of voice that stopped Papyrus's words. "i don't know who the other parent is. leave it alone."

"I REALLY THINK YOU SHOULD PURSUE THIS FURTHER, BUT I SHALL RESPECT YOUR WISHES ON THE MATTER. I DO STILL HAVE A QUESTION THOUGH. DO YOU NEED TO TOUCH AT ALL FOR THIS SOUL BONDING TO HAPPEN?

"you need to be close enough for your souls to bond. touching helps. but i think just being around each other for extended periods of time is enough." Sans tried to remember anything Gaster had told him, but he'd always made it seem like soul bonding outside of sex was rare, and children even rarer. "why? worried the same thing will happen to you? i'm surprised it even happened to me."

"I'M NOT WORRIED. I WAS JUST THINKING." Papyrus flapped his hand, as if that would chase away whatever thought was plaguing him. "ANYWAY, IT IS ABOUT TIME FOR ME TO START DINNER. I FOUND A NEW RECIPE TO TRY. YOU TAKE NOODLES, THEN PUT THEM IN A POT OF BROTH, AND THEN ADD SLICES OF BEEF AND VEGGIES. IT SEEMS LIKE A WEIRD WAY TO MAKE SPAGHETTI, BUT THE PEOPLE ONLINE SEEMED ADAMANT THAT IT WAS TASTY."

"sounds soup-er."

"YES, IT DOES INDEED SOUND... THAT WAS A PUN, WASN'T IT?"

**Notes for the Chapter:**

> Papyrus is a joy to write, and I hope everyone has as much fun reading him as I had writing him.

**Author's Note:**

> No idea if I'll continue this. Would anyone want to see more of this? I kind of want to write more just so you can meet the baby, but for right now, this is complete.
> 
> As a side note, I was listening to the Undertale soundtrack while writing and formatting this. As I was going to hit post, Flowey's manical laughter came up. Is that a sign? Quite possibly.
> 
> Last edited to fix some typos. I swear, they multiple when I'm not looking.


End file.
